Say hello to hologram RAM

Japanese researchers have finally figured out how to plug the data leak that is preventing the widespread use of holographic memory -- a high-density, high read speed storage optical system that works on the same principle as the 3D security labels on credit cards. Holographic memory itself isn't new. Just as a visual hologram can record a complete three-dimensional object in a single sheet of photographic film, it can also be used to store data to a very high density. The data is written with a laser beam which pulses on and off to represent binary 1s and 0s. A second beam crosses the first at a set angle generating an interference pattern -- a pattern that's recorded in a special storage material as positive and negative charges. Whole stacks of interference patterns can be laid on top of each other, each pattern being produced by setting the first, data laser and the second, reference beam at different angles. Reading the data back is simply a matter of shining a laser onto the material. It interacts with the interference pattern to reproduce the original pulsing data beam. The snag has always been that the process of reading back the interference pattern -- and thus the data -- over time changes those charges, in the process damaging the information stored. According to science journal Nature, the Japanese team solved the problem by adding iron and a rare metal called terbium to the standard lithium niobate storage material. Terbium becomes coloured when it's exposed to ultraviolet light and, more to the point, once coloured this way helps the lithium niobate retain its data-encoding charges. The team, from the National Institute for Research in Inorganic Materials in Tsukuba, claims the modified storage medium will retain data without deterioration for up to two years if it's not exposed to light, and that it holds data safely for at least nine hours if the information is constantly exposed to a read laser. Clearly there's still someway to go before holographic memory becomes a practical reality -- who wants to re-archive all their data every two years? -- but it is a major step toward that goal. ® Related StoriesBoffins beat Moore's Law with quantum magicStorage tech boffins to demo 140GB 'CD-ROM'US researchers develop molecular memoryUK boffins unveil $35 '2300GB on a PC Card' RAM breakthrough